fix: (getByText) more robust null/undefined check for text children

[hduprat]

Summary

When the number 0 is integrated into a component via a variable, getByText('0') does not find any Text instance.

Examples

Example.jsx:

const test = 0;
...
<Text>{test}</Text>

Example.test.jsx:

const testInstance = render(<Example/>);
getByText('0'); // throws whereas it should not, as there is a 0 in a text component

Test plan

A test has been added in render.test.js

[vonovak]

Suggested change

	child => (child !== undefined && child !== null ? child.toString() : '')
	child => (child ?? child.toString() : '')